This invention relates to fluid valves.
Utilization of coil springs as valving means for fluids is known in the art and is taught in British Pat. No. 1,217,538. However, because of nonuniformities usually present in coil springs it is difficult if not impossible to economically manufacture a fluid-tight coil spring. Swedish Pat. No. 153,362 teaches that sealing between adjacent turns of coil springs can be provided by coating the spring with rubber. However, because of the configuration of a coil spring, a uniform coating thereon providing a fluid-tight relationship between adjacent convolutions of the coil spring is difficult to achieve in production at an economical cost.
Inasmuch as metallic springs are manufactured by coiling a suitable wire, residual stresses are induced in the springs and must be relieved. The stress relieving procedure involves heating the coiled spring to an elevated temperature and keeping the spring at that temperature for a predetermined time period. Stress relief temperatures, of course, vary with the spring wire being utilized and can range from about 400.degree.F. for music wire or oil-tempered steel wire to about 850.degree.F. for 18-8 stainless steel wire. From the foregoing it is readily apparent that an elastomeric coating applied to a spring prior to coiling and stress relief will be destroyed during the subsequent stress relieving operations, yet it is extremely difficult to apply a uniform coating to a spring after stress relief.
It is an object of the present invention to obviate the aforementioned problems and to provide a manufacturing method whereby a substantially uniform, resilient outer sheath, rather than a coating, is applied to an already stress-relieved, coiled spring.
It is a further object of this invention to provide an improved fluid valve means which is capable of regulating the flow of fluids with a reduced pressure drop across the valve means.
Yet another object of this invention is to provide a long-lasting fluid valve means which requires very little force for actuation.
Still further objects of this invention will readily present themselves to the skilled artisan upon reference to the ensuing specification, the drawing and the claims.